Batteries are widely used as a means of power supply for electric equipment, and these batteries include primary batteries such as manganese batteries, alkaline manganese batteries and zinc-air batteries, and secondary batteries such as nickel cadmium (Ni—Cd) batteries, nickel hydrogen (Ni-MH) batteries and lithium ion batteries.
Currently, most widely used secondary batteries are lithium ion batteries, however, there are still many problems to be solved, and many limits such as relatively low theoretical energy unit density and natural lithium reserves have been revealed. Accordingly, with the needs for a next generation secondary battery that may replace lithium ion secondary batteries, which is capable of saving manufacturing costs while exhibiting high performances, a metal-air battery such as a lithium-air battery has been proposed.
A lithium-air battery has energy density 10 times higher than existing lithium ions batteries, and exhibits efficiency that matches the efficiency of gasoline, thereby is capable of significantly reducing the volume and the weight of a battery.
Theoretical energy density of a lithium-air battery is 3,000 Wh/kg or greater, and this corresponds approximately 10 times of the energy density of lithium ion batteries. Moreover, a lithium-air battery has advantages in that it is environmental-friendly and are more stable compared to lithium ion batteries, however, there are still many problems to be solved for commercialization, which include charge and discharge life span, efficiency improvement and the like.
Accordingly, researches on the commercialization of a lithium-air battery have been required.